Percussive rock drill



United States Patent T 3,055,441 PERCUSSIVE ROCK DRILL William A.Morrison, Easton, Pa., assiguor to Ingersoll- Rand Company, New York,N.Y., a corporation f New Jersey Filed Nov. 6, 1958, Ser. No. 772,332

8 Claims. (Cl. 175-139) This invention relates to percussive rock drillsof the type employing a rotation mechanism including a rifle bar and anassociated pawl and ratchet device, and it has for its object to preventrifle bar failure in such a drill under severe rotational strain.

Another object of the invention is to provide a novel and improvedresilient connection between the rifle bar and the ratchet holdingmechanism in a rock drill of the above type.

Another object is to provide such a resilient connection between theparts of a two-piece chuck driver in a drill of the type specified,either as an alternative or supplement to the resilient connectionbetween the rifle bar and the ratchet holding mechanism.

Still another object is to provide such a resilient connection orconnections having inexpensive and easily replaceable shear pins whichwill fail under extreme load conditions before any damage occurs to therifle bar in a drill of the type specified.

Various other objects and advantages will be apparent as the nature ofthe invention is more fully disclosed.

The rotating mechanism of conventional percussive rock drills usuallyincludes a fluted rifle bar having a head carrying pawls engageable withthe ratchet teeth of a fixed ratchet ring. The rifles of the barcooperate with a rifle nut fixed in the head of the hammer piston, sothat during each stroke of the piston in one direction the piston ismade to rotate while the rifle bar pawls are engaged with the teeth ofthe ratchet ring, while during each piston stroke in the other directionthe rifle bar is made to rotate while its pawls ride over the teeth ofthe ratchet ring.

Serious difliculty has been encountered with the rifle bar breakage invarious rock drills of the above type, which is usually caused byconditions requiring operation of the drill at full throttle to withdrawa tight bit from the drilled hole. Under such conditions, the shock loadand strain are taken on the very end of the rifle bar and breakagefrequently results.

The present invention overcomes the above difliculty 'by providing anovel torsionally resilient joint in either one or both of two locationsin a rock drill of the foregoing type. One of such locations is betweenthe stem of the rifle bar and the head of said bar, while the other isbetween the parts of a two-piece chuck driver which, through theintermediary of the chuck, rotates the drill rod. As a result of suchconstruction, suddenly applied shock load is gradually applied and isdistributed over the full bearing of the rifle nut instead of beingconcentrated in a small part of the bar as before.

In one embodiment disclosed herein for the purposes of illustration, thetorsion-opposing joint mentioned above comprises a plurality of pinswhich are seated in mating holes in the rifle bar stem and the toothedratchet member. These holes are tapered as hereinafter described toprovide hollows into which the pins can bend under the torsional forceimparted to the rifle bar by the piston of the rock drill. As a result,this torsional force is applied to the rifle bar more gradually thanheretofore, permitting it to rotate to a limited extent without beingtwisted. Under extreme load conditions said pins, which are inexpensiveand easily replaceable, will shear 011 before the rifle bar can bedamaged. In the other embodiment Patented Sept. 25, 1962 hereinafterdescribed, the resilient pins connect the two parts of the two-piecechuck driver, but the operation is the same in both embodiments of theinvention.

The invention is described more in detail in connection with thepreferred embodiments illustrated in the accompanying drawing, in which:

FIG. 1 is a broken longitudinal sectional view of a rock drill embodyingthe invention;

FIG. 2 is a transverse section through the rifle bar and associatedparts, taken on line 22 of FIG. 1; and

FIG. 3 is a transverse section through the chuck driver and associatedparts, taken on line 33 of FIG. 1.

The drawing shocks a rock drill cylinder 1 having a bore or chamber 2containing the usual reciprocable hammer piston 3 for delivering impactblows to the shank of a conventional drill rod as hereinafter described.

Any conventional valve structure 4 may be used to supply air throughpassages 5 and 6 to reciprocate the piston 3. The exhaust passage isillustrated at 7 in FIG. 1.

As is customary in rock drills of this type, a rotation mechanismoperated by the hammer piston is provided for rotating the drill steelas the latter is percussively actuated. This rotation mechanism includesa rifle bar 8 having a spirally fluted or splined lower end portionslidingly interlocked with a rifle nut 9 fixed within the head of thepiston.

The annular head 10 at the top of cylinder 1 carries pivotally mountedsets of pawls 12 which are urged inwardly by air operated plungers 13into engagement with the teeth 14 of ratchet ring member 15. The ring 16serves to hold one or the other of each set of pawls out of action asthe ratchet moves in one direction or the other.

In accordance with one embodiment of the invention, a plurality ofcylindrical steel pins 17 provide a torsionally resilient or elasticconnection between the rifle bar 8 and the toothed ratchet ring member15. These pins 17, here shown to be six in number, are seated in matingholes 18 and 19 which are equally spaced about the flange 2d of riflebar 8 and the adjacent surface of ratchet ring member 15, respectively.The holes 18 and 19 are taper-ed longitudinally so that they are widerat their mating inner ends than they are at their outer ends. The saidwide regions of holes 18 and 19 thus form enlarged hollows into whichthe cylindrical pins 17 can bend under the influence of the torsionalforce presently to be described.

With the spiral flutes or splines of the rifle bar 8 inclined in thedirection shown in FIG. 1, the rifle bar will tend to rotate clockwisein FIG. 2 during each return stroke of the piston 3. However, suchrotation of the rifle bar is prevented by the operative engagement ofcertain pawls 12 with the teeth 14 of ratchet ring member 15, as shownin FIG. 2. As a result, piston 3 is caused to rotate, and this rotationis in turn transmitted to the drill steel in a manner well understood inthe art. During each down stroke of the piston, rotation in acounter-clockwise direction in FIG. 2 is imparted to rifle bar 8, butthe pawls 12 ride over the teeth 14 of ratchet ring member 15, or overthe ring 16, so that the piston 3 moves axially without rotating.

0n the return stroke of piston 3, as described above, the piston isrotated as the ratchet mechanism holds the rifle bar 8 against rotation.The torsional force im parted to the rifle bar by the piston at thistime is applied much more gradually than it otherwise would be becausethe pins 17 will bend or flex into the tapered holes 18 or 19 and thuspermit rotation (about five degrees) of the rifle bar without any twistof the bar. In practice the piston will travel approximately one-fifthof its return stroke during the period the pins 17 are flexed to themaximum extent. This means that the turning force is applied moregradually to the rifle bar than when the rifle bar is held rigidlyagainst rotation.

The rock drill shown in FIG. 1 has a chuck driver which is made in twoparts 22 and 23. The rear or upper part 23 of said chuck driver has asplined connection with the nose of piston 3 at 24 and rotatestherewith. This rotation is transmitted from the chuck driver to thechuck 25 which in turn rotates the drill rod 26. In accordance with theinvention, torsionally resilient cylindrical pins 27, here shown to besix in number (FIGS. 1 and 3), are seated in mating holes 28 and 29which are equally spaced about the adjacent surfaces of chuck driversections 22 and 23, respectively. As in the case of the holes 18 and 19previously described, the holes 28 and 29 are tapered so that they arewidest at their mating ends, thus affording enlarged hollows into whichthe pins 27 can bend under the influence of the above-describedtorsional force. The operation is the same as that described above inconnection with the rifle bar and ratchet joint.

The above-described action is particularly important when the drill isrunning on so-called cushion, i.e., when the drill is operated but thedrilling tool or bit is not in contact with the rock. At such time thepiston does not strike the working implement but its forward motion ishalted by air trapped in the chamber 2. At this time the piston travelsforward a greater distance than during normal operation and accordinglya shorter length on the rifle bar 8 is in engagement with the rifle nut9. In the absence of the flexible connection between the rifle bar andthe ratchet holding mechanism, and/or the flexible connection betweenthe two sections of the chuck driver, an extremely high load would beapplied to the tip of the rifle bar at the time the piston is reversed.

The pins 17 and 27 herein described also act as shear pins when anextreme load condition is encountered on the rifle bar, the pins in suchcase being weaker than the rifle bar or the chuck driver and failingbefore any damage occurs to the rifle bar. The pins are cheap and easilyreplaced.

Although certain specific embodiments have been shown and describedherein for purposes of illustration, it will be evident to those skilledin the art that the invention is capable of various modifications andadaptations within the scope of the appended claims.

The invention claimed is:

1. In a rock drill, the combination with a cylinder having a pistonreciprocable therein, :of a rotation mechanism for said piston includinga rifle bar extending into said piston, spiral means on said barcoacting with spiral means within said piston, a head surrounding theouter portion of said rifle bar, a rotatable ring associated with saidrifle bar within said head, means for rotationally locking said ring inone direction to said head, and a plurality of resilienttorsion-opposing pins connecting said rifle bar to said ring.

2. In a rock drill, the combination with a cylinder having a pistonreciprocable therein, of a rotation mechanism for said piston includinga rifle bar extending into said piston, spiral means on said barcoacting with spiral means within said pistons, a fixed annular headsurrounding the outer portion of said rifle bar, a rotatable ringconcentric with said rifle bar within said annular head, means forrotationally locking said ring in one direction to said head, matingholes in said rifle bar and said ring, and pins in said holes lockingsaid rifle bar and said ring in rotational engagement with each other,said holes being enlarged in parts to permit said pins to bend therein.

3. In a rock drill, the combination with a cylinder having a pistonreciprocable therein, of a rotation mechanism for said piston includinga rifle bar extending into said piston, spiral means on said barcoacting with spiral means within said piston, a fixed annular headsurround- 4 ing the outer portion of said rifle bar, a rotatable ringconcentric with said rifle bar within said annular head, means forrotationally locking said ring in one direction to said head, matingholes in said rifle bar and said ring equally spaced about the axis ofsaid rifle bar and ring, and pins in said holes locking said rifle barand said ring in rotational engagement with each other, said holes beingtapered longitudinally and being widest at their mating ends to formhollows into which said pins can bend under applied torsion-a1 force.

4. In a rock drill, the combination with a cylinder having a pistonreciprocable therein, of a rotation mechanism for said piston includinga rifle bar extending into said piston, spiral means on said barcoacting with spiral means within said piston, a ratchet mechanismincluding a fixed annular head surrounding the outer portion of saidrifle bar, a rotatable ratchet ring concentric with said rifle barwithin said annular head, ratchet teeth on the outer annular edge ofsaid ratchet ring, spring biased pawls carried by said annular head andengageable with said ratchet teeth to rotationally lock said ratchetring in one direction to said head, mating holes in said rifle bar andsaid ratchet ring equally spaced about the axis of said rifle bar andratchet ring, and pins in said holes locking said rifle bar and saidratchet ring in rotational engagement with each other, said holes beingwidened at their mating ends to permit said pins to flex transverselytherein.

5. In a rock drill, the combination with a cylinder having a pistonreciprocable therein, of a chuck driver rotatably and slidably connectedto said piston, a drill rod rotated by said chuck, a rotation mechanismfor said piston including a rifle bar extending into said piston, spiralmeans on said bar coacting with spiral means within said piston, aratchet mechanism including a fixed annular head surrounding the outerportion of said rifle bar, a rotatable ratchet ring concentric with saidrifle bar within said annular head, ratchet teeth on the outer annularedge of said ratchet ring, pawls carried by said annular head andengageable with said ratchet teeth to rotationally lock said ratchetring in one direction to said head, mating holes in said rifle bar andsaid ratchet ring equally spaced about the axis of said rifle bar andratchet ring, and pins in said holes locking said rifle bar and saidratchet ring in rotational engagement with each other, said holes beingtapered longitudinally and being widest at their mating ends to formhollows into which said pins can bend under applied torsional force.

6. In a rock drill, the combination with a cylinder having a pistonreciprocable therein, of a chuck driver composed of two members, onemember having a connecting portion connected to said piston to resistrelative rotation therebetween while permitting relative longitudinalmovement, the other member having a connecting portion connected to adrill rod for rotation therewith, a rotation mechanism for said pistonincluding a rifle bar extending into said piston, spiral means on saidbar coacting with spiral means within said piston, a head surroundingthe outer portion of said rifle bar, a rotatable ring associated withsaid rifle bar within said head, means for rotationally locking saidring in one direction to said head, means connecting said rifle bar tosaid ring, each of said members having holes for receiving resilienttorsion-opposing means for connecting the two members of said chuckdriver.

7. In a rotary driving mechanism having a bore con taining areciprocable hammer piston for delivering impact blows to the shank of adrill rod of a rotary percussive rock drill, the combination comprising:

(a) ahead,

(b) a ratchet ring rotatably disposed in said head and having an outerperimeter edge,

(0) said ratchet ring having ratchet teeth disposed on said outerperimeter edge and spring biased pawls carried by said head andengageable with said 6 ratchet teeth to rotationally lock said ratchetring in (g) resilient pins disposed within said longitudinally onedirection to said head, tapered holes and to secure said rotation meansand (d) rotation means rotating said hammer piston to said ratchet ringin rotational engagement with each thereby rotate said percussive rockdrill, and other. (e) pins means between said rotation means and said 5ratchet ring to gradually apply and to evenly dis- References cued m thefile of thls patent tribute sudden shock load therebetween. UNITEDSTATES PATENTS 8. The rotating driving mechanism according to claim 5 5,2 w Sept 19 1393 7 including said pins means in which: 1,148,649 BaylesAug. 3, 1915 (f) said rotation means and said ratchet ring are pro- 102,439,479 Mackmann Apr. 13, 1948 vided with longitudinally taperedholes, and 2,737,818 Feucht Mar. 13, 1956 UNITED STATES PATENT UFFICECERTIFICATE OF CORREQTIUN Patent No. 3,055,441 September 25, 1962 IWilliam A. Morrison It is hereby certified that error appears in theabov e numbered patent requiring correction and that the said LettersPatent should read as corrected below In the grant, line -l,

. name of inventor, for "William A.

Norrison" read William A. Morrison column 2, line 13,

for "shocks" read shows column 3, line 63, for "pistons" read pistonSigned and sealed this 5th dey of February 1963.

(SEAL) Attest:

ERNEST W. SWIDER DAVID LADD Attesting Officer Commissioner of Patents

